Apparatus for conveying information from a moving object to a stationary object

ABSTRACT

A warning device associated with a rotatable body comprising means on the rotatable body for creating a magnetic field, a receiving coil on a relatively stationary member arranged such that upon rotation of the rotatable body interaction with the magnetic field causes electrical pulses to be generated in the receiving coil and an electronic switching circuit operated by the pulses such that a warning is given upon occurrence of a predetermined condition such as pressure or temperature of a vehicle wheel deviating outside a predetermined limit.

[1 1 3,840,850 Oct. 8, 1974 United States Patent [191 ing et al.

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/1967 Nilssen........................... 3/1968 8/1971 [5 APPARATUS FOR CONVEYING 3,093,812 6/1963 INFORMATION FROM A MOVING OBJECT 3 32 2% TO A STATIONARY OBJECT [76] Inventors: Roland Graham Whitein Massoubre.....

Brumbelow 3,614,732 10/1971 Lejeune 3,659,734 5/1972 Fuzzell....

3,662,335 5/1972 Fritze 3,665,387 5/1972 Enabnit.......

3,691,524 9/1972 Frost et g, Duncan Rd., Johannesburg; Johannes Godfried Antonius van Mill, 12 Lucas Rd., Edenvale, both of South Africa May 11, 1972 [22] Filed:

Primary Examiner-John W. Caldwell Assistant Examiner-Joseph E. Nowicki Attorney,

Appl. No.: 252,227

Agent, or Firm-Cushman, Darby & Cushman [30] Foreign Application Priority Data Dec. 17, 1971 South Africa.......................

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[56] References Cited rence of a predetermined condition such as pressure UNITED STATES PATENTS g outslde or temperature of a vehicle whee1 deviatin predetermined limit.

0/53 8 Claims, 9 Drawing F lgures 2,269,083 1/1942 Langsam et 2,475 533 7/1949 Varner................

PAIENTEDBET.

SIEEIZOF 3 APPARATUS FOR CONVEYING INFORMATION FROM A MOVING OBJECT TO A STATIONARY OBJECT This invention relates to a method and apparatus for conveying information, generally in connection with the physical state of a moving and generally rotating body, from the moving body to a relatively stationary object and more particularly but not exclusively, the invention is concerned with warning devices adapted to be actuated when the physical state of a moving body or part thereof deviates from a certain or desired physical state.

Still more particularly but not exclusively, the invention relates to a self-generating safety or warning device for use on wheeled vehicles having pneumatic tires such as motor cars, road transport vehicles and aircraft having landing wheels, the device being adapted to warn the person in charge of the vehicle that the tire pressure or temperature has deviated outside a predetermined safe range.

In the case of wheeled vehicles fitted with pneumatic tires and particularly road transport vehicles having double wheel assemblies, large costs are often incurred in purchasing new tires, owing to the fact that the vehicle has had a flat tire without the driver being aware thereof in sufficient time to avoid irreparable damage to the tire. In the case of double wheel assemblies, both tires are often irreparably damaged owing to the sidewalls of the two tires rubbing against each other.

In any event, in the case of any motor vehicle, a dangerous situation can arise where tire pressures of wheels fall below a certain minimum.

In order to detect such flat or soft tires, slip-ring assemblies, radio transmitters and sonic devices have been proposed for transmitting information from the wheels to the axle of a vehicle but these, as far as applicants are aware, have either not been successful and/or have been extremely costly.

In other fields, such as in the case of machinery, it is often important to be warned of alterations in the physical state of rotatable bodies such as, for example, the speed of rotation of a body either per se or in relation to the speed of rotation of another body.

It is accordingly the object of this invention to provide a method and apparatus for transferring information from a movable body to an adjacent relatively fixed body as well as a warning system incorporating such transmission method and apparatus which operates effectively and is relatively inexpensive.

In accordance with this invention there is provided a self-generating method of transmitting information from a moving body to a stationary member adjacent the moving body comprising locating on the moving body means for creating a magnetic field which is arranged to co-act with at least one receiving coil on the stationary member to create pulses of electrical current therein upon movement of the body and processing the pulses to achieve a desired objective, the pulses being created at a frequency proportional to the velocity of the moving body relative to the stationary member and the generation of the pulses further being optionally dependent on a physical condition of a part or the whole of the moving body.

Further features of the invention provide for the magnetic field to be created either intermittently or continuously, for the moving body to be a rotating one and that in the case where the physical condition of the rotating member is the speed of rotation thereof. the frequency of pulses created is compared electronically with a reference chain of pulses optionally created in like manner by a second rotating member, for the electronic comparison of these chains of pulses to be arranged to give a signal should the frequencies differ to any predetermined extent and for the two rotating members to be parts of a transmission drive of a vehicle on the input and output sides thereof.

In the case where information about other physical conditions is required, for example, the temperature of a part of the rotating body or the tire pressure in the case of a wheel carrying a pneumatic tire, the invention provides for the magnetic field to be created intermittently by a magnet on the stationary member co-acting with a first coil on the rotating member, the first coil being connected in series or parallel with a second coil which is arranged to co-act with the receiving coil on the stationary member, the circuit on the rotating member including a sensing device (such as a temperature or pressure operated switch) arranged to initiate or terminate the creation of pulses depending on the physical condition sensed by the sensing device.

The above and other features of the invention will become apparent from the'following description of various embodiments of the invention, reference being made to the accompanying drawings in which:

FIG. 1 is a diagrammatic illustration of a tire pressure sensing arrangement;

FIG. 2 is a block diagram illustrating the functions of eachpart of the circuit of the arrangement;

FIG. 3 is a circuit diagram of a complete circuit of the arrangement;

FIG. 4 is aplan view of an annunciator panel to be used in the arrangement;

FIG. 5 is a sectional elevation of a tire valve assembly for use in the arrangement;

FIG. 6is a sectional isometric view of a unit to be secured to a wheel;

FIG. 7 is an elevation of the inside of a wheel carrying the unit of FIG. 5;

FIG. 8 is a cross-section through a wheel showing the mounting of the coils and magnet; and

FIG. 9 is a diagrammatic illustration of a simple version of the warning device.

In the embodiment of the invention illustrated in FIGS. 1 to 8, a receiver unit 1 is fitted to a stationary part of a vehicle adjacent each of the wheel assemblies thereof. As illustrated in FIG. 8, this may be done with the aid of a support 2 secured to the axle 3 associated with each wheel assembly. Alternatively, the receiver unit may be secured to a brake-shoe supporting disc of a drum brake assembly if this is more convenient. Each of these receiver units embodies a magnet 4 which may be either an electroor a permanent magnet and a receiving coil 5 connected into a control circuit which is described below. Preferably, the magnet and receiving coil are embedded or encapsulated in a suitable material to prevent damage thereto by stones, dust, water, snow, mud and the like thrown up by the vehicle during driving thereof, and further to prevent corrosion.

A transmitter unit 6 ismounted on each wheel assembly 7 to rotate therewith. In the present embodiment the transmitter units are of arcuate shape, as shown in FIG. 6 and are arranged to be fitted to a wheel 8 on the inside thereof in the manner of a balancing weight.

However, where each receiver unit is secured to a brake-shoe supporting disc, the transmitter unit will be secured to the associated brake drum. In either case each pair of associated units are arranged such that upon rotation of a wheel the transmitter unit closely passes the receiver unit once per revolution.

Each transmitter unit 6 in this embodiment comprises two coils 9 and 10, the ends of which are electrically connected to form an electrical loop which is interrupted by a sensing switch, in this case a pressure switch 11 arranged to be operated by the pressure of the associated tire. Again these coils are embedded or encapsulated in suitable material to prevent damage thereto during use. This pressure switch is arranged to be closed when the tire pressure is above a predetermined minimum but to open upon the tire pressure falling below such minimum value.

Each tire is thus provided with a valve fitting 12 which is fitted onto the existing valve lug after removal of the valve itself therefrom, a complementary socket 13 being provided on the fitting for this purpose. The fitting is tubular in shape and is supplied at its end remote from the socket with a valve 14 and intermediate its ends is a branch 15 to which is secured the pressure switch 11.

To enable this switch to be connected into the loop which includes the two coils, leads 16 passing through a tube 17 extending from the transmitter unit are provided, the tube passing through a hole in the wheel and being provided with a sealing cap 18 which seals over the pressure switch. The leads 16 are electrically connected to the two terminals 19 of the pressure switch.

Finally, a reed switch 20 is connected across the one coil 10 of the transmitter unit, the function of the reed switch being to create a large back E.M.F. by the opening of this switch at a predetermined time when the two units of a pair are passing each other, the reed switch being operated by the magnet such that it is moved from its normally open position to a closed condition prior to its re-opening which causes the back E.M.F. This back E.M.F. results in a large pulse being created in the two coils of the transmitter unit which in turn results in a readable pulse being created in the receiver coil 5 of the receiver unit as a consequence of the magnetic field caused by the pulse in the transmitter coils.

In the case of a double wheel assembly, only one pair of units will be provided in general with the pressure switch on each tire being connected into the loop formed by the two coils in the transmitter unit. These two switches will be connected in series in the case of the present embodiment but will be connected in parallel in the simple version described hereinafter.

Referring now to FIG. 2, each receiver coil 5 is connected to the input of an amplifier 21, the output of which is fed to a timer circuit 22 which is adapted to give a negative output when more than a predetermined number of pulses per second are received from the amplifier. For the description of this circuit negative is earth and thus positive refers to the logic indication 1 and negative to the logic indication 0. In this case the timer circuit is arranged to give a negative output if more than one pulse per second is received thereby and a positive output if less than one pulse per second is received thereby. The output from the timer circuit is fed to a digital control circuit which is interconnected with a second digital control circuit fed by an amplifier 21a and timer circuit 22a connected to the receiver coil 5a associated with another wheel on the vehicle, this other wheel conveniently being the corresponding wheel on the other side of the vehicle.

In each case the digital control circuit comprises two invertors and a NOR gate in series, the output from the first invertor 23, 23a being connected to the input of the second invertor 24, 24a and to the one input of the NOR gate 25a, 25 of the other circuit, the output from the second invertor 24, 24a being connected to the other input to the associated NOR gate 25, 25a.

The NOR gate thus operates such that the output therefrom is always negative while at least one input thereto is positive, and the output is only positive if both inputs to the NOR gate are negative.

The output from the NOR gate 25, 25a is fed to a delayed trigger 26, 26a which is arranged to fire an electronic switch-27, 27a in the form of a silicon controlled rectifier (SCR). Each SCR is arranged to close a circuit to a red light bulb 28, 28a and simultaneously to switch off a common green light bulb 29 and to activate a buzzer 30 which is connected into the circuit such that it may be isolated by a switch 31 (see FIG. 3) if desired.

It will be understood that a comparison of signals is thus effected at the NOR gate, this comparison being such that the following outputs from the NOR gates are obtained:

a. While pulses are received from both receiving coils 5 and 5a one input to each NOR gate is positive and thus the output from that NOR gate is negative.

b. When pulses are created in only one receiving coil, say that indicated by numeral 5a, both inputs to the NOR gate 25a associated with this receiving coil 5a are negative thus causing the NOR gate 250 to have a positive output. This is fed to the delayed trigger 26a. This trigger is arranged to take about 2 seconds to fire the SCR and thus after 2 seconds the SCR 27a will be fired. Since the fault (i.e., the absence of pulses) is in the other receiving coil circuit, the SCR 270 is connected to close the circuit of the red light bulb 28 associated with the other circuit thus giving a correct location of the fault.

c. When pulses are created in neither coil, which will be the case when the vehicle is stationary, again one input to each NOR gate is positive and no red light bulbs will be illuminated, since no output is obtained from either NOR gate.

The full circuit diagram is illustrated in FIG. 3 from which it will be seen that the various circuits described with reference to the block diagram are as follows:

a. The circuit of the amplifier 21 comprises a common emitter single stage transistor amplifier of conventional design.

b. The circuit of the timer comprises a first transistor 32, the base of which is connected to the output from the amplifier 21 and which is arranged to intermittently charge an electrolytic capacitor 33 according to the frequency of pulses received by the first transistor 32. This capacitor 33 biases a second transistor 34 in such a way that the output of this transistor is negative when the capacitor is charged. Thus if the frequency of the pulses received by the first transistor 32 is insufficient to maintain the capacitor in a charged condition, the second transistor 34 will stop conducting and the output from this transistor 34 will become positive. The values of the components of this timer circuit are chosen to allow a time delay of about one second without the output from the second transistor 34 going positive.

c. The first invertor 23 comprises a transistor 35 which is arranged to reverse the polarity of the sig nal received from the timer circuit and provide the correct polarity of the one input to the NOR gate 25a in the other circuit.

d. The second invertor comprises a transistor 36 which again reverses the polarity of the signal to provide an input to the NOR gate of the original polarity of the output from the timer circuit.

e. The NOR gate comprises a transistor 37 having the I f. The delayed trigger comprises a unijunction transistor 40, the emitter of which is connected to the output from the NOR gate 25. This unijunction is delay biased byan electrolytic capacitor 41 connected between earth and the emitter. The unijunction will conduct on a predetermined voltage on the emitter being attained which will occur when the capacitor 41 has been charged sufficiently. The time delay is thus dependent on the value of a resistor 42 connected between the emitter of the unijunction and the positive supply and through which the capacitor is charged.

The timer circuit further comprises a pair of resistors 43 and 44 which are interconnected through the bases of the unijunction, these resistors acting as a voltage divider when the unijunction conducts. The output from the unijunction is connected to the gate of the SCR 27 which is connected into the power supply to the appropriate red light bulb 28.

The capacitor 41 in the trigger circuit is arranged to take about two seconds to fire the unijunction, thus, since one pulse per revolution is created by the coils and these pulses cannot be more than 360 out of phase, a light cannot possibly go on while all is in order unless the difference in the speed of rotation of the pair of wheel assemblies is greater than one revolution .per two seconds. This is unlikely'to occur unless a wheel is seized or the brake drag on a wheel is at least substantial.

The red light bulbs 28, 28a are located on an annunciator panel 45 (see FIG. 4) which is illuminated and depicts a mimic diagram of the wheel pattern of the vehicle such that the bulb behind the appropriate wheel will light up in the event of a low pressure tire or in the event of a brake seizure.

It will be seen from the circuit diagram that a red light bulb, once lit will remain in this condition until a cancel switch 46 in the circuit is depressed whereupon the SCR will return to a non-conducting condition owing to the fact that the anode voltage of the SCR is removed.

This circuit also includes a test switch 47 for firing the SCRs which will cause illumination of all the red light bulbs 28 in order to test the circuit. Since the connection between the gates of the SCRs and the test switch will be common, each gate is connected to the test switch through a separate diode 48 which thus prevents all the SCRs being fired when one .is fired due to a fault.

Furthermore, the green light bulb 29 is located behind the panel 45, this bulb being arranged such that the panel glows a green colour while all is in order.

This green light bulb is supplied through an electronic switch in the form of a transistor 49 which switches the light off immediately the circuit of a red light bulb is switched on whether or not the red light bulb is in an operative condition or not. This, therefore, provides an extra safeguard against blown light bulbs. If a circuit of a blown red light bulb is closed the green light goes off and by pressing the test button all red lights will go on except for the blown bulb so that the location of the fault will again be known.

Finally, this circuit is also provided with the audible alarm in the form of the buzzer 30 which may be switched to an operable or inoperable position as required by the two position switch 31.

In use, when the vehicle is stationary, both timer outputs of a pair of wheels will be positive and thus, owing to the digital control circuit no red light bulbs will be illuminated, although no pulses are received by the amplifiers.

When the wheels are turning and not more than one revolution per 2 seconds difference in speed of rotation exists between them, pulses will be created by the magnet in the closed coil circuit of the transmitter unit, these pulses being transmitted by the resultant magnetic fields to the stationary receiver coils 5, 5a which in turn maintain the timer outputs negative.

If during driving of the vehicle the pressure in a tire decreases below a certain minimum, the pressure switch associated with the tire will open, thereby terminating the generation of the intermittent magnetic field on that transmitter unit and thus also terminating the train of pulses to the amplifier. The output from the appropriate timer will go positive, thus giving rise to the appropriate SCR being triggered and the red warning light going on, thus giving an immediate warning of a tire with low pressure.

It will be appreciated that many variations may be made to the above-described embodiment of the invention without departing from the scope of the invention.

Thus, as in the case of the simplified embodiment illustrated'in FIG. 9, the pressure switches may be arranged to allow a chain of pulses to be created in a stationary receiving coil 50 only in the event of an undesirably low pressure being detected. In this case, the pulses could simply be amplified if necessary by an amplifier 51 and used toswitch a bulb 52 on directly by way of an SCR 53 without comparison with another signal, thus obviating the necessity of the digital control circuits. In order to achieve this, the pressure switch 54 in the transmitter unit could be connected in parallel to the reed switch 55 (i.e., across the ends of each coil 56 and 57). Thus under normal conditions a short circuit exists between the ends of the coils, this short circuit opening in the case of a fault developing. Thus, no comparison is required, since pulses are not generated when all is in order and the vehicle is stopped.

This simplified version may also be provided with a green light bulb 58 to indicate that all is in order and a two position switch 59 allowing a buzzer 60 to be included in parallel with the red light bulb or to be isolated as desired. The green light bulb will again go off when a red light bulb is illuminated, one red light again being provided for each wheel behind an annunciator 10 panel if desired.

The above embodiments of the invention could also be used to warn of high temperatures in tires on aircraft or other vehicles, for example, the pressure switch simply being replaced by, or connected in series with, a temperature switch. Also, by providing double action switches predetermined high and low conditions may be sensed and a warning given thereof.

While the receiving coil and magnet in the case of the receiver unit and the two coils in the case of the transmitter unit have been described as being adjacent each other, they could be off-set angularly to any desired extent provided they still interact correctly. In the extreme case they would be 1 80 offset, in which case two pulses per revolution could be obtained by providing a reed switch across each of the coils in the transmitter unit. Of course, any desired number of pulses per revolution may be obtained in a manner which will be clear to those skilled in the art.

It will be understood that the temperature or pressure switches above referred to could be replaced by any other sensing switch adapted to open or close, as the case may be upon the desired physical condition of the rotating member or a part thereof, deviating outside a predetermined limit.

Also, the arrangement may be applied to any rotating member other than a wheel, for example, parts of mechanical machinery or the like.

Where the speed of rotation of a body is of concern, the same system as above described could be used with the omission of the sensing switch; in this case the comparison being between the frequency of the pulses against a reference frequency. The reference frequency could be that of a similarly created chain of pulses created by a member which is to rotate at the same speed as the body. Thus the body could be one part of a clutch or other power transmission chain and the other member another part thereof, thereby constituting a device for warning of slippage. In the case of a vehicle clutch, the device may be arranged to be turned off during gear changes. In this case, the source of magnetic field on the rotating members could, since they need never be switched off, be permanent magnets which would replace the closed coil circuits and magnet on the stationary'member. A similar system could be designed to sense loss of angular movement in belt transmission systems, or actual revolutions as in the case of lathe operations which are preferably carried out at predetermined speeds. Also, a system could be designed for regulating the speed of propellors on multi-engined aircraft relative to each other.

It will be understood that there are numerous other applications to which the invention could be put, the

basis being the transmission of information utilizing 6 jects or reciprocating or oscillating objects such as lifts, mine hoists or railway lines, for example.

What we claim as new and desire to secure by Letters Patent is:

l. A warning device associated with a movable body comprising:

transmitter means mounted on said body to move therewith, said transmitter including first and second electrically interconnected coils located in spaced relationship;

a condition-responsive switch electrically interconnected with said coils whereby a circuit is completed through the coils dependent upon the position of the switch;

receiver means mounted on a stationary body adjacent said movable body, said receiver including a third coil located proximate the second coil when the first coil is located proximate a magnetic field source mounted on said stationary body, said source being capable of inducing a current in said first coil when proximate said first coil;

a magnetically operated switch connected in parallel with said first coil and operated by said source as current is induced in said first coil so as to produce a back E.M.F. which is inductively coupled by the second coil to said third coil when said conditionresponsive switch is positioned to complete a circuitthrough said first and second coils; and

means joined to said third coil and responsive to the level of voltage induced on the third coil for providing a warning upon occurrence of a condition which changes the position of said conditionresponsive switch.

2. A warning device as set forth in claim 1, wherein said movable body is rotatable.

3. A warning device as set forth in claim 1, wherein said first and second coils are connected in series with the condition-responsive switch.

4. A warning device as set forth in claim 1, wherein said magnetically operated switch is a normally open reed switch which is closed when the first coil is located proximate said source.

5. A warning device as set forth in claim 1, wherein said condition-responsive switch is responsive to pressure.

6. A warning device as set forth in claim 1, wherein said condition-responsive switch is responsive to temperature.

7. A device for detecting the movement of a movable body, comprising:

transmitter means mounted on said body to move therewith, said transmitter including first and second electrically interconnected coils located in spaced relationship;

receiver means mounted on a stationary body adjacent said movable body, said receiver including a third coil located proximate the second coil when the first coil is located proximate a magnetic field source mounted on said stationary body, said source being capable of inducing a current in said first coil when proximate said first coil;

a magnetically operated switch connected in parallel with said first coil and operated by said source as current is induced in said-first coil so as to produce a back E.M.F. which is inductively coupled by the second coil to said third coil to produce a pulse thereon; and

means joined to said third coil for sensing pulses induced on said third coil.

8. A device as set forth in claim 7, wherein said movable body is rotatable. 

1. A warning device associated with a movable body comprising: transmitter means mounted on said body to move therewith, said transmitter including first and second electrically interconnected coils located in spaced relationship; a condition-responsive switch electrically interconnected with said coils whereby a circuit is completed through the coils dependent upon the position of the switch; receiver means mounted on a stationary body adjacent said movable body, said receiver including a third coil located proximate the second coil when the first coil is located proximate a magnetic field source mounted on said stationary body, said source being capable of inducing a current in said first coil when proximate said first coil; a magnetically operated switch connected in parallel with said first coil and operated by said source as current is induced in said first coil so as to produce a back E.M.F. which is inductively coupled by the second coil to said third coil when said condition-responsive switch is positioned to complete a circuit through said first and second coils; and means joined to said third coil and responsive to the level of voltage induced on the third coil for providing a warning upon occurrence of a condition which changes the position of said condition-responsive switch.
 2. A warning device as set forth in claim 1, wherein said movable body is rotatable.
 3. A warning device as set forth in claim 1, wherein said first and second coils are connected in series with the condition-responsive switch.
 4. A warning device as set forth in claim 1, wherein said magnetically operated switch is a normally open reed switch which is closed when the first coil is located proximate said source.
 5. A warning device as set forth in claim 1, wherein said condition-responsive switch is responsive to pressure.
 6. A warning device as set forth in claim 1, wherein said condition-responsive switch is responsive to temperature.
 7. A device for detecting the movement of a movable body, comprising: transmitter means mounted on said body to move therewith, said transmitter including first and second electrically interconnected coils located in spaced relationship; receiver means mounted on a stationary body adjacent said movable body, said receiver including A third coil located proximate the second coil when the first coil is located proximate a magnetic field source mounted on said stationary body, said source being capable of inducing a current in said first coil when proximate said first coil; a magnetically operated switch connected in parallel with said first coil and operated by said source as current is induced in said first coil so as to produce a back E.M.F. which is inductively coupled by the second coil to said third coil to produce a pulse thereon; and means joined to said third coil for sensing pulses induced on said third coil.
 8. A device as set forth in claim 7, wherein said movable body is rotatable. 